The present invention relates to a vertical type wafer supporting jig for mounting many wafers onto many support plates stacked superposed on one another with a predetermined wafer mounting interval being provided among them, whereby the support plates are fixed to a plurality of support pillars extending in a vertical direction.
Semiconductor supporting jigs are used for holding many semiconductor wafers aligned, and particularly, vertical type wafer supporting jigs are suitable for a so-called wafer supporting boat for use in transporting wafers into and out of a wafer heat treatment apparatus.
In a semiconductor production process in which is used a wafer treatment apparatus for performing drive-in treatment comprising placing semiconductor wafers (which is sometimes referred to simply as xe2x80x9cwafersxe2x80x9d) inside a heating furnace surrounded by a heater, and allowing impurities to permeate inside the wafer by heating under a high temperature atmosphere in a temperature range of from about 400 to 1400xc2x0 C. while flowing gaseous raw material together with a predetermined carrier gas, conventionally used are cassette boats for supporting the wafers aligned and mother boat or a wafer support boats (supporting jigs) for mounting thereon a plurality of said cassette boats, and these are denoted collectively as wafer supporting jigs.
The wafer supporting jigs are suitable for handling a plurality of thus supported wafers in one unit in each process step, and, in general, processing of the wafers is performed together with the wafer supporting jig, for instance, in the heat treatment step as described above, or in a cleaning step using, for example, hydrofluoric acid as the cleaning liquid. Thus, by taking chemical stability and heat resistance into consideration, generally used as the material for the wafer supporting jigs is quartz glass, silicon, or compounds thereof.
For instance, the vertical type wafer supporting jig 100 shown in FIG. 7 and FIG. 8 comprises a top plate 112 and a bottom plate 114 on the upper and the lower ends thereof, and a plurality (i.e., four, in the example shown in the figure) of support pillars 116a to 116d are attached thereto by welding. A number of ring-like support plates 118 corresponding to the number of the wafers to be placed in the apparatus are attached, by welding, to the plurality of support pillars 116a to 116d arranged in the vertical direction and set apart exactly from each other. A plurality (e.g., 3 pieces) of wafer supporting protrusions are provided on the upper plane of said ring-like supporting plate 118 by taking proper distance from each other, and the wafers W are mounted on the support plate 118 via the wafer supporting protrusions 120.
Problems the Invention is to Solve
However, in producing the vertical type wafer supporting jig 110 of a conventional type, care should be made by taking the size of the wafers W to be handled; for instance, the bottom plate 114 of each of the supporting member inside each of the wafer supporting jig is taken as the standard, and the position set at a distance from the standard plane for attaching each of the supporting plates should be set within the dimensional allowance, or the top plate 112 and the bottom plate 114 should be held within the axial degree allowance, i.e., the allowance in tilting degree with respect to the central axis, etc.
Furthermore, since the wafer supporting jigs 110 in use are handled in units with wafers and are subjected to various types of treatments, they are under danger of suffering from thermal deformation, a change with passage of time due to degradation, melting, wear damage, etc., attributed to the use of cleaning solution on cleaning treatment, or to breakage due to careless operator.
Wafer supporting jigs 110 are made from an expensive material having high chemical stability, and in case even one support plate should require replacement among the many support plates (e.g., 50 wafer support plates per single wafer supporting jig) constituting the unit, the welded old support plates should be cut off and removed by using a cutter and the like, and then a new one should be heated for welding. Such a repair treatment is not easily afforded from technical and economical viewpoint, because it may impair the precision of attachment of the constituting support members around the replaced one.
In particular, the support plates that are used in wafer support jigs frequently subjected to heat treatment tend to cause deformation at higher rates as compared with wafer support jigs used in other processes. In case of a defect attributed not only to a single support member, and requires replacement of plural support plates or repair of the deformed member, the wafer supporting jig should be newly fabricated at a large expense.
Accordingly, the problems of the vertical type wafer supporting jig 110 above are, that there is difficulty in carrying out the welding work while retaining dimensional precision of each member due to the working on fabrication; and, since the support plate 118 is relatively thin with respect to its planar size because the thickness thereof is determined in correspondence with the wafer, that the welding requires high skill because the portions other than the welding position are subject to thermal deformation on welding the support plates to the pillars 116a to 116d. Furthermore, in the repair working, there is fear of causing defects on the surrounding sound support plates 118 on repairing the defective support plate 118 by welding or by thermal treatment. Accordingly, there are other problems as such that a highly skilled technique is required for the repair, that the repair cost becomes costly, etc.
In the light of the aforementioned disadvantages of the prior art technology, there have been proposed a vertical type wafer enclosing jig (Japanese Utility Model Laid-Open No. 45332/1994) or a heat treatment board (unexamined published Japanese patent Laid-Open 237781/1997) employing a non-welding method for fixing the support plates. However, although these proposed methods for fixing the support plates are improved in that they do not use welding, they still had to be simplified in operations for fixing the support plates.
The present invention has been made with an aim to further improve the above methods for fixing the support plates. The present invention provides a vertical type wafer supporting jig which does not employ the conventional welding means for fixing the ring-like support plates to the pillars, which enables fixing the support plates by a simple structure that surely preventing the falling off of the ring-like support plates from occurring, and which also is capable of rapidly cope with the demand of repair.
Means for Solving the Problems
In order to solve the above problems of generic vertical type wafer supporting jig, it is suggested by the present invention that support groove portions for inserting and supporting the support plates are formed in the support pillars with a predetermined interval between them, a fixing rod is provided extending along at least one of the support pillars, whereby in a peripheral part of the support plates at least one receiving groove is provided, said receiving groove is provided to engage the fixing rod, and the support plates are fixed to and supported by the support pillars by means of causing each of the support plates to be inserted into and supported by the support groove portions and causing the fixing rod to be fitted to the at least one receiving groove of each of the support plates.
By using the vertical type wafer supporting jig according to the present invention, there is no need of welding the support plates during the assembly process of the wafer supporting jig as required in the conventional technique, and thereby the wafer supporting jig can be completed by a simple assembly; hence, there is no fear of impairing the dimensional precision or of requiring high skill not only on assemblage but also on repair. In particular, the single support plate that is produced under strict quality control itself assures the quality of the wafer supporting jig. Further, the repair can be completed by a simple exchange of the support plate, the repair can be rapidly accomplished without impairing the other sound support plates, and a repair service of high quality can be provided at a low cost and yet, without impairing the function of the wafer supporting jig.
Preferably, two fixing rods are provided adjacent to two support pillars on the side of inserting the support plates of the plural support pillars above, and by further providing two receiving grooves to the peripheral parts of said support plates in correspondence to said fixing rods in such a manner that said support plates can be inserted to the support groove portions and held thereby and causing the two fixing rods to be fitted to the two receiving grooves of the corresponding support plates so as for the support plate to be fixed to and supported by the support pillars, the inserted support plates can be advantageously supported and fixed surely by the two support pillars.
Mode of Practicing the Present Invention
An embodiment according to the present invention is described below based on the attached FIGS. 1 to 6. However, it should be understood that the case shown in the figures are provided only as examples, and that various modifications can be made thereto so long as they do not deviate from the technical concept of the present invention.